In floating gate EPROMs, one of the historic areas of concern has been data retention. In MOS transistors, the most common type of passivation that has been used is phosphosilicate glass (PSG) which has been used on EPROMs. The PSG has been found to lead to data loss due to moisture penetration. If the EPROM is in a ceramic package, which is hermetically sealed, the problem is lessened. The problem is greater in a plastic package, which is not hermetically sealed, than in ceramic. Similarly, the problem is more severe for devices which are not packaged, eg. left in wafer form, than for ones in plastic packages. The use of a nitride passivation has been found to improve the data retention, presumably because it is a better barrier to moisture than PSG. Nitride as passivation, however, creates other problems. Typical nitride absorbs ultra-violet (UV) radiation. The UV radiation, which is required to erase EPROMs, does not effectively penetrate this type of passivation which is quite thick, for example, 3000 Angstroms. This type of nitride passivation is relatively effective for one time programmable (OTP) ROMs. There is also a type of a UV-transparent nitride and there is oxynitride which have been used to benefit. All of these, however, also have problems with stress-induced metal voids which is not a problem with PSG.